Estimation

Estimation is the calculated approximation of a result which is usable even if input data may be incomplete or uncertain.

In statistics,

In mathematics, approximation or estimation typically means finding upper or lower bounds of a quantity that cannot readily be computed precisely.

In signal processing, see estimation theory for approximating an unobserved signal on the basis of an observed signal containing noise.

In project management, see estimation (project management) for applications to project planning.

In physics, a Fermi problem is one concerning estimation in problems which typically involve making justified guesses about quantities that seem impossible to compute given limited available information.